Optical filter with dichroic crystals that reduces reflected light by 1.3–1.4 stops and eliminates surface reflections.
Polarizers use dichroic crystals or stretched polyvinyl alcohol films that can be aligned at a 90° angle to each other. Standard diameters range from 52mm to 112mm for camera lenses. The transmission for optimally aligned CPL filters is between 38-42%, corresponding to a light loss of 1.3-1.4 stops. Linear polarizers can interfere with autofocus systems, which is why only circular variants are used in digital cinematography. The filter ring is rotatably mounted, allowing for stepless adjustment of the polarization direction.
The first polarizer was developed by Edwin Land in 1928 and patented in 1938 under the name "Polaroid." Kodak introduced the first cinematic polarizers for 35mm cameras in 1947. In the 1960s, CPL filters became established with the proliferation of single-lens reflex cameras. With digitalization from the 1990s onwards, manufacturers like B+W, Hoya, and Tiffen developed multi-coated filters with 99.9% polarization efficiency.
Terrence Malick extensively used CPL filters in "Days of Heaven" (1978) for the golden wheat field shots to eliminate reflections and increase color saturation. For water shots, the filter reduces surface reflections and makes underwater details visible – a technique used in "Life of Pi" (2012) for the ocean sequences. Automotive sequences benefit from the reduction of windshield reflections, as seen in the driving scenes of "Baby Driver" (2017). The filter enhances sky contrasts without color shift, which is crucial for available-light shooting.
Polarizers differ from ND filters in their selective light effect – they only reduce reflected light, not the overall exposure. UV filters offer contrast enhancement but no reflection reduction. Modern digital post-production can increase contrast but can only remove physical reflections with difficulty. Graduated neutral density filters address exposure differences, while polarizers address surface reflections. Variable ND filters use two opposing polarizing layers but produce cross-polarization artifacts at extreme settings. Matte boxes with filter holders allow the combination of polarizers and other filters without vignetting.
Ich setze CPL-Filter primär bei Exteriors mit Wasser oder Glas ein, um Reflexionen kontrolliert zu eliminieren und die Tiefenwirkung zu verstärken. Der 1,3-Blendenstufen-Verlust zwingt mich zur präzisen Belichtungsmessung, aber die Farbsättigung ohne Post-Grading ist unschlagbar. Bei rotierenden Objektiven wie Zooms montiere ich den Filter in der Matte-Box, um konstante Polarisation zu gewährleisten.
Ich nutze Polfilter gezielt für emotionale Momente, wo kristallklare Bilder ohne störende Reflexionen die Aufmerksamkeit auf die Performance lenken. Bei Dialogen im Auto eliminiert der Filter Armaturenbrett-Spiegelungen komplett, wodurch die Gesichter der Schauspieler ungestört wirken. Himmel und Wasser erhalten durch den Filter eine fast hyperrealistische Qualität, die perfekt zu dramatischen Wendepunkten passt.
CPL-Filter kosten zwischen 150-800€ je nach Objektivdurchmesser und reduzieren VFX-Aufwand für Reflexionsentfernung erheblich. Der Zeitgewinn am Set durch wegfallende Reflexions-Setups kompensiert die 1-2 Drehtage Mehrkosten für zusätzliche Beleuchtung. Ich kalkuliere Standard-CPL-Sets für alle Brennweiten ein, da nachträgliche Reflexionsretusche das 10-fache der Filterkosten verschlingt.
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